1. Field of the Invention
The present invention relates to medical instruments and more particularly relates to the trachael tube having a self-inflating and self-deflating trachael cuff portion. Even more particularly, the present invention relates to an endotrachael or tracheotomy tube having a cuff portion which seals off the flow of fluids other than through the tube itself during inhalation of the patient, the cuff self-deflating during exhalation of the patient, withdrawing any contact with the trachael wall.
2. General Background and Prior Art
Tubes are utilized often by surgeons to ventilate a patient's lungs. These tubes generally are of two types depending on their structure and use. The first type of tube is referred to generally as an "endotracheal" tube. An endotracheal tube requires generally that insertion of the tube be through an upper airway, such as the mouth, nose or trachea. The use of an endotracheal tube does not contemplate an incision into the trachea of the patient for its insertion.
A second type of tracheal tube is called a tracheostomy tube and requires that an incision be made in the neck region at the base of the throat and extending into the inner wall of the trachea. A tracheotomy thus allows insertion of the tube through the trachea wall rather than an upper airway in order to properly ventilate the lungs.
In the case of either an endotracheal tube or a tracheostomy tube, both tubes generally utilize a "cuff" which is a structure provided at the generally distal end portion of the tube. The cuff functions as a sealing member which inflates or is inflated in order to form a seal between the tube and the wall of the trachea. Thus, during ventilation of the patient, only air flow through the center of the tube occurs thereby negating the chance for inadvertent and undesireable escape of air from the lungs. If the tube is then connected to a ventilating apparatus or resuscitator, the flow of air will be governed by the resuscitator since a seal will have been perfected with the wall of the trachea.
A further use for the cuff portion of the endotracheal or tracheostomy tube is seen. This is the isolation of the flow of fluids between the respiratory organs of the individual patient and the stomach and esophagus. It is essential that the stomach and esophagus be separated from the respiratory organs in order to prevent the inadvertent flow of stomach acids and like undesireable fluids from the stomach into the esophagus and into the trachea and lungs. Such a mixture of stomach acids and like fluids with the respiratory tract produces an undesireable "aspiration" which can complicate proper breathing of the patient.
Tracheal cuffs, per se, are known. Several tracheal tubes are on the market which in one way or another are provided with cuffs which attempt to properly seal the trachea between the trachael wall and the tracheal tube, thus only allowing the flow of air between the attached resuscitator and lungs. These prior art devices suffer from several inadequacies.
Prior art devices sometimes maintain a seal between the tracheal tube and the tracheal wall at all times. This is undesireable as it maintains an inadvertently high pressure against the trachea producing a "necrosis". Further, it has been found that when the pressure is high enough to perform the desired seal, there is an interruption of the blood circulation in the trachea tissue which can produce lesions upon the walls of the trachea.
Some prior art devices have attempted to solve this problem by periodically deflating the cuff in order to permit momentary circulation of blood through the tissues surrounding the cuff. This however, requires a highly skilled person who must no only perform the decompression of the cuff at the proper time, but at the proper pressure. If the deflation is excessive, the tracheal tube will not retain the proper seal and difficulty in the patient's breathing will result.
U.S. Pat. No. 3,769,983 issued to Abraham Merav and entitled "Medical Devices" provides a self-inflating tracheal tube which is of an "umbrella" fashion. The Merav device provides an open end which has an opening to the outer portion of the trachea between the tracheal tube and the cuff itself. This is undesireable, because the flow of mucous which normally proceeds in both directions up and down the tracheal wall can easily enter the cuff, filling it and halting its proper operation.
U.S. Pat. No. 3,616,799 issued to C. H. Sparks and entitled "Tubes with Sail Cuffs for Tracheal Intubation" provides such a similar umbrella type structure.
U.S. Pat. No. 3,709,227 issued to R. H. Hayward entitled "Endotracheal Tube with Positive Check Valve Air Seal" provides another umbrella type cuff which suffers from the aforementioned mucous accumulation and mucous build up problems.
While some patents have taught away from the use of an open ended or umbrella type cuff, they suffer from other problems which the prior art has failed to solve but which are solved by the present invention. U.S. Pat. No. 4,020,849 issued to R. R. Jackson and entitled "Cuff Inflation for Trachael Tubes" provides a cuff which has no openings between the cuff wall and endotracheal tube. Thus, it does not suffer from the problems of mucous accumulation as do the aforementioned patents. However, the Jackson patent provides a means for always retaining the cuff in an inflated position. This is undesireable, even though the cuff is inflated by air of the same pressure as is used to ventilate the lungs. At first, it will appear that such a device will never inflate to a pressure greater than the pressure of air used to fill the lungs of a patient during inhalation. However, if the patient were to cough or otherwise discharge an explosive force of air, air could enter the cuff and retain it thereafter in an overly inflated position for a time. Another U.S. Patent to R. R. Jackson entitled "Self-Inflating Endotracheal Tube" (U.S. Pat. No. 3,707,151) makes another attempt at solving the problems of reducing excessive pressure on the tracheal wall and stopping the flow of fluids from the stomach and esophagus into the lungs. In FIGS. 1 and 2 of U.S. Pat. No. 3,707,151, there is seen a self-inflating cuff which utilizes only the air flowing through the tracheal tube for its inflation. However, the Jackson device attempts to retain the cuff in an inflated position during exhalation of the patient. The '151 patent provides a check valve which seals the openings provided between the air conveying tube and the tracheal wall when air is being discharged from the trachea as is illustrated in FIG. 3 of U.S. Pat. No. 3,707,151.
These and other problems are discussed in an article appearing in "Annals of Surgery" Volume 184, No. 2, August 1976. In that article entitled "Tracheo-innominate Artery Erosion", the applicant of the present invention co-authors an article which analyzes the problem of tracheo-innomiate artery erosions.
The use of a check valve in order to seal the cuff in an inflated position during exhalation is dangerous since it allows excessive bursts of air to enter and be trapped within the cuff, the check valve closing with the high pressure air retained with no way for ventilation. Such could be the case, for example, if the patient were to cough expelling air from the lungs at increased pressures, pressures above the pressure of air being used to ventilate the patient.
Other attempts at the aforementioned problems which have perplexed the art but have yet been solved are further seen in other U.S. Patents, the following table of which is a listing. The following table provides a listing of some patents of which the applicant of the present invention is aware.
______________________________________ PRIOR ART PATENTS U.S. PAT. NO. INVENTOR ISSUE DATE ______________________________________ 3,481,339 J. A. Millet Puig Mar. 28, 1969 3,504,676 V. N. F. Lomholt June 13, 1967 3,616,799 C. H. Sparks Oct. 8, 1969 3,707,151 R. R. Jackson Dec. 26, 1972 3,709,227 R. H. Hayward Jan. 9, 1973 3,769,983 A. D. Merav Nov. 6, 1973 3,794,036 R. G. Carroll Feb. 26, 1974 4,020,849 R. R. Jackson May 3, 1977 ______________________________________
3. General Discussion of the Present Invention
The present invention provides a device which solves all the prior art problems and shortcomings in a simple manner with a relatively inexpensive and uncomplicated structure. The device provides a cuff which self-inflates during inhalation of the patient using only the air that is used to ventilate the patient and using air at the same pressure. During exhalation of the patient, the cuff is promptly self-deflated, thereby removing pressure on the tracheal wall. Since the air utilized to inflate the lungs is likewise utilized to inflate the cuff, pressure on the trachea wall is sufficient but no grater than the pressure needed to form a substantially fluid tight seal with the trachea wall. During exhalation, a seal with the tracheal wall is not necessary,, as a seal is only necessary during inhalation of the patient. In order to solve the problem of the inadvertent travel of stomach acids and like undesireable fluids from the stomach and esophagus to the trachea and lungs, an obturator is provided for insertion above the implanatation point for the tracheal tube. The obturator provides the function of halting the flow of fluids in the trachea in a transverse direction.
The self-inflating and self-deflating feature of the cuff portion of the invention is provided by utilizing a valving means in the form of a path of lesser resistance of air into the tracheal cuff. It is desireable and it is provided with the present invention that air flow firstly into the tracheal cuff, (during inhalation) and firstly out of the tracheal cuff (during exhalations) by following a path of least resistance. In the preferred embodiment, the path of least resistance is provided in the form of an increased diameter opening between the tube wall and the tracheal cuff. Thus, the flow of air within the tracheal tube is firstly routed into the cuff before its travel in the tube itself. In the preferred embodiment a single opening is provided, however, a plurality of openings providing an overall lesser resistance for flow into the cuff rather than flow in the tube is of importance.